Heat energy recovery

ABSTRACT

A heat energy recovery system for an engine, and a vehicle having an engine and a heat energy recovery system. The heat energy recovery system has a liquid supply, one or more evaporators, an expander, a condenser, and a port. The one or more evaporators are fluidly connected to the liquid supply and configured to heat liquid to a superheated vapour using heat energy from an engine. The expander is fluidly connected to the one or more evaporators and configured to be driven by the superheated vapour. The expander has an expander outlet. The condenser has an inlet fluidly connected to the expander outlet. The port is upstream of the condenser inlet and configured for injection of liquid from the liquid supply to reduce the temperature of fluid entering the condenser. The port is further configured for injection of liquid between the expander outlet and the condenser inlet.

TECHNICAL FIELD

The embodiments described below relate to heat energy recovery systems, and more particularly, to a vehicle waste heat recovery system.

BACKGROUND OF THE INVENTION

Internal combustion (IC) engines are used throughout the world and mainly for motor vehicles. IC engines account for one of the largest consumers of fossil fuels known. Due to the large amount of fossil fuels consumed by IC engines and the gases exhausted from IC engines, numerous regulatory agencies have implemented regulations or are in the process of implementing regulations that require minimum average fuel economy of vehicles as well as limit the amount of pollutants that are exhausted from vehicles.

It is generally known that only about thirty to forty percent of the energy produced by the fuel combustion of IC engines translates to mechanical power. Much of the remaining energy is wasted in the form of heat. Therefore, one particular area of focus in the motor vehicle industry has been to recover some of the heat that is generated by the IC engine using a Rankine cycle.

U.S. Pat. No. 4,031,705 discloses a heat energy recovery system as shown in simplified form in FIG. 1. Working fluid from a reservoir 20 is pressurized by pump 22 (using work W) and passed to an evaporator where it is vaporized using heat H from the exhaust of an IC engine 5 and the IC engine's cooling circuit, i.e., the IC engine's radiator, before passing it through an expander 12 from which mechanical work M is output. A bypass valve 14 is provided that allows vapor to be directed via a bypass connection 16 into a condenser 18 rather than through the expander. Although this is typically not a problem for lower temperature and/or pressure vapors, as the temperature and/or pressure increases, the shock to the condenser caused by receiving superheated vapor can reduce the life expectancy of the condenser. Condenser 18 supplies liquid back to the reservoir 20, the energy released on condensation being ejected at V.

WO2014/060761 (incorporated herein by reference) discloses a waste heat recovery system as shown in simplified form in FIG. 2A. As with the embodiment of FIG. 1, the system comprises a supply 20 of liquid, for example liquid ethanol, a pump 22, one or more evaporators 10 in fluid communication with the liquid supply and receiving waste heat FI from an engine. Where there are plural evaporators 10′,10″, these may be arranged in series or in parallel controlled by a control or diverter valve 114 as shown in FIGS. 2B and 2C respectively. A bypass valve 14 includes an inlet port 30 in fluid communication with an outlet of the one or more evaporators, a first outlet port 31 in fluid communication with an expander 12 and a second outlet port 32 in fluid communication with a condenser 18. The second outlet port includes an injection port 40 in fluid communication (via line 39 and pump 22) with the liquid supply 20. By injecting the superheated vapor with liquid from the liquid supply, thus de-superheating the working fluid, a substantially cooler working fluid can be provided to the condenser, which reduces the thermal shock to the condenser.

Another benefit follows from the fact that super-heated vapor is dry and hence a poor thermal conductor: de-super heating re-saturates the vapor, making it wet and finally liquid, in which conditions it transfers heat much more readily, allowing the surface area of the condenser and thus its size to be reduced. Another benefit is that other construction methods or materials may be used for the condenser. This enables, inter alia, lower weight, lower cost and higher thermal conductivity than conventional condensers of stainless steel. In a particular embodiment, the injection port is a venturi that receives liquid from the pump via a ‘de-superheat’ control valve. This valve may be integrated into a control module that also incorporates the control/diverter valve for the evaporators. A simple pipe junction of fixed flow dimension may also be used in place of the venturi.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention, there is provided a heat energy recovery system for an engine (5), comprising:

-   -   a liquid supply (20);     -   one or more evaporators (10) fluidly connected to the liquid         supply and configured to heat liquid to a superheated vapor         using heat energy from an engine (5);     -   an expander (12) fluidly connected to the one or more         evaporators and configured to be driven by the superheated         vapor, the expander having an expander outlet (13);     -   a condenser (18) having an inlet (19) fluidly connected to the         expander outlet (13); and     -   a port (41;70) upstream of the condenser inlet (19) and         configured for injection of liquid from the liquid supply (20)         to reduce the temperature of fluid entering the condenser;     -   wherein the port (41;70) is configured for injection of liquid         between the expander outlet (13) and the condenser inlet (19).

The system may comprise a bypass circuit having a bypass inlet (14′) fluidly connected to the one or more evaporators and a bypass outlet (15) fluidly connected to the condenser (18), the bypass outlet (15) and the expander outlet (13) being fluidly connected at a junction (17) at or upstream of the condenser inlet (19).

The port (41) may be configured for injection of liquid between the expander outlet (13) and the junction (17).

The system may comprise a further port (40) configured for injection of liquid between the bypass outlet (15) and the junction (17).

The port (70) may be configured for injection of liquid downstream of the junction (17).

The system may further comprise a pump (22) configured to feed liquid from the liquid supply (20) to the one or more evaporators (10), the port (41;70) having a fluid connection (61) to the liquid supply (20) via the pump (22).

The further port (40) may have a further fluid connection (60) to the liquid supply (20) via the pump (22).

The connection (61) and/or further connection (60) may comprise a flow control valve.

The connection (61) and/or further connection (60) may have a flow path of fixed dimensions

According to a second aspect of the invention, there is provided a heat energy recovery system for an engine (5), comprising:

-   -   a liquid supply (20);     -   one or more evaporators (10) configured to heat liquid to a         superheated vapor using heat energy from an engine (5);     -   a pump (22) configured to feed liquid from the liquid supply         (20) to the one or more evaporators (10);     -   an expander (12) fluidly connected to the one or more         evaporators and configured to be driven by the superheated         vapor, the expander having an expander outlet (13);     -   a condenser (18) having an inlet (19) fluidly connected to the         expander outlet (13); and     -   a port (40) upstream of the condenser inlet (19) and configured         for injection of liquid from the liquid supply (20) to reduce         the temperature of fluid entering the condenser;     -   wherein the port (40;41) has a fluid connection (50) to the         liquid supply (20) upstream of the pump (22).

The system may comprise a bypass circuit having a bypass inlet (14′) fluidly connected to the one or more evaporators and a bypass outlet (15) fluidly connected to the condenser (18), the bypass outlet (15) and the expander outlet (13) being fluidly connected at a junction (17) at or upstream of the condenser inlet (19).

The port (40) may be configured for injection of liquid between the bypass outlet (15) and the junction (17).

The port (41) may be configured for injection of liquid between the expander outlet (13) and the junction (17).

The system may comprise a first port (40) configured for injection of liquid between the bypass outlet (15) and the junction (17) and a second port (41) configured for injection of liquid between the expander outlet (13) and the junction (17).

The first and second ports (40,41) may be fluidly connected to the liquid supply via a further junction (55).

The further junction (55) may be downstream of the fluid connection (50).

The first port (40) may have a first fluid connection (50′) to the liquid supply (20) and the second port (41) may have a second fluid connection (50″) to the liquid supply (20), the first and second fluid connections (50′, 50″) being connected downstream of the further junction (55).

The fluid connection (50; 50′, 50″) may comprise a flow control valve.

The fluid connection (50; 50′, 50″) may have a flow path of fixed dimensions.

The fluid connection (50; 50′, 50″) may comprise a pump, which may be a jet pump.

According to another aspect, there is provided a vehicle having an engine and a heat energy recovery system as set out above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 3 is a schematic of a first embodiment of a heat recovery system for an engine according to a first aspect of the invention;

FIG. 4A is a schematic of a second embodiment of a heat recovery system for an engine according to a first aspect of the invention;

FIG. 4B is a schematic of a third embodiment of a heat recovery system for an engine according to a first aspect of the invention;

FIG. 4C is a schematic of a fourth embodiment of a heat recovery system for an engine according to a first aspect of the invention;

FIG. 5 is a schematic of a first embodiment of a heat recovery system for an engine according to a second aspect of the invention;

FIG. 6 is a schematic of a second embodiment of a heat recovery system for an engine according to a second aspect of the invention;

FIG. 7 is a schematic of a third embodiment of a heat recovery system for an engine according to a second aspect of the invention

DETAILED DESCRIPTION OF THE INVENTION

The figures and following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a heat recovery system. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the system. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

FIG. 3 illustrates a first aspect of a heat energy recovery system 1 for an engine according to the present invention and in which a liquid—in this case ethanol—from a supply 20 is conveyed by pump 22 to one or more evaporators 10 configured to heat liquid to a superheated vapor using heat energy from an engine. An expander 12 is fluidly connected at its inlet 12′ to the one or more evaporators and is configured to be driven by the superheated vapor, the outlet 13 of the expander fluidly communicating with a condenser 18 which supplies liquid back to the supply/reservoir 20. It will of course be appreciated that the outlet may be a point within the physical structure of the expander but downstream of the point of maximum expansion.

A bypass valve 14 having inlet 14′ allows superheated vapor to bypass the expander via a bypass valve outlet/bypass circuit inlet 15 connected to a bypass circuit 32. The outlets 13,15 of the expander 12 and bypass valve 14 connect at a junction 17 at or upstream of the condenser inlet 19. Supplied via pump 22 and connection 60 (which may be a valve), liquid from the reservoir 20 is injected into the bypass circuit 32 upstream of the condenser at 40 so as to reduce the temperature and/or enthalpy of the fluid entering the condenser.

In addition to connection 40 in the line 32 between the outlet 15 of the bypass valve 14 and the inlet 19 of the condenser 18, there is provided a further connection 41 in the line 33 to allow liquid to be injected between the outlet 13 of the expander 12 and the inlet 19 of the condenser, thereby reducing the temperature and/or enthalpy of the working fluid leaving the expander. Connection 41 is fed from a further connection 61 in the line 62 between the outlet 23 of the pump 22 and the inlet 11 to the evaporator(s) 10. Connection 61 may be separate from connection 60, as shown, or may be combined in a single component such as a valve. Moreover, connection 61 may be a simple pipe junction having a flow path of fixed dimensions allowing constant flow (not necessarily constant flow rate) or a valve controlling flow (again, not necessarily constant flow rate). Connection 60 may similarly be a simple pipe junction rather than a valve.

FIG. 4A illustrates a development of the previous arrangement, identical features being indicated by identical reference numbers. Instead of separate connections for injection of liquid downstream of the outlets 13,15 of the expander and bypass valve 12,14, a single connection 70 is provided downstream of the junction 17 of flow from the expander outlet 13 and bypass valve outlet 15. Connection 70 is supplied with liquid via a single connection 61 in line 62 as described above.

FIG. 4B illustrates a further development, identical features being indicated by identical reference numbers. Bypass valve outlet 15 is connected to the lower pressure end 13′ of the expansion machine 12 so as to allow that superheated vapor that would otherwise bypass the expansion machine to discharge into the machine. Consequently, bypass valve 14 acts as a diverter. Discharge into the lower pressure end of the machine (downstream of the higher pressure inlet 12′ when the machine is being driven) allows the machine to be warmed and/or purged during start-up but without driving the machine as happens when the superheated vapor is diverted by valve 14 to the higher pressure inlet 12′ of the machine. On leaving the expansion machine, the fluid is then injected with liquid at connection 70 as in the embodiment of FIG. 4A.

FIG. 4C illustrates a further development of the arrangement of FIG. 4B, identical features being indicated by identical reference numbers, in which bypass valve 14 is integrated into the expansion machine 12. Similarly, ports 40 and 41 may be integrated into a single component, which may itself be integrated into the bypass valve 14 and/or the expander 12. FIG. 5 illustrates a further aspect of the invention, identical features being indicated by identical reference numbers. Instead of the liquid injected at 40 being supplied via the pump 22 that supplies the evaporator(s) 10, it is supplied via an additional connection 50 to the reservoir. Connection 50 may be a pipe allowing constant flow (not necessarily constant flow rate), a valve controlling the flow (again, not necessarily constant flow rate) or an additional pump. As regards connection 40, this may be a simple pipe junction or may comprise a venturi nozzle and/or a jet pump.

FIG. 6 illustrates a development of the previous arrangement, identical features being indicated by identical reference numbers. Like the previous arrangement, the liquid to be injected for reducing the temperature and/or enthalpy of the fluid entering the condenser is supplied via an additional connection 50 to the reservoir. Connection 50 may be a pipe allowing constant flow (not necessarily constant flow rate), a valve controlling the flow (again, not necessarily constant flow rate) or an additional pump, which may be a jet pump. However, like FIG. 3, connection 50 not only supplies to a connection 40 for injection of liquid in the line 32 between the outlet 15 of the bypass valve and the inlet 19 of the condenser 18, it also supplies (via junction 55, downstream of connection 50) to a connection 41 for injection of liquid in the line 33 between the outlet 13 of the expander 12 and the inlet of the condenser. Connections 40,41 may be simple pipe junctions or may comprise a venturi nozzle and/or a jet pump.

FIG. 7 illustrates a development of the arrangement of FIG. 6 in which connections 40,41 are each supplied via respective connections 50′,50″ connected via a common junction 55 to an outlet 21 of the liquid reservoir 20 such that the connections are downstream of junction 55. Connections 50′, 50″ may each be a pipe allowing constant flow (not necessarily constant flow rate), a valve controlling the flow (again, not necessarily constant flow rate) or an additional pump, which may be a jet pump. Connections 40,41 may be a simple pipe junction or may comprise a venturi nozzle and/or a jet pump.

Within the second aspect of present invention is also included a development (not shown) of the embodiment of FIG. 4 in which liquid is taken from upstream rather than downstream of the pump 22.

Although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. Particular features of embodiments of each aspect may be applied to embodiments of other aspects. The teachings provided herein can be applied to other heat energy recovery systems, and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the embodiments described above should be determined from the following claims. 

1. A heat energy recovery system for an engine, comprising: a liquid supply; one or more evaporators fluidly connected to the liquid supply and configured to heat liquid to a superheated vapor using heat energy from an engine; an expander fluidly connected to the one or more evaporators and configured to be driven by the superheated vapor, the expander having an expander outlet; a condenser having an inlet fluidly connected to the expander outlet; and a port upstream of the condenser inlet and configured for injection of liquid from the liquid supply to reduce the temperature of fluid entering the condenser; wherein the port is configured for injection of liquid between the expander outlet and the condenser inlet.
 2. The heat energy recovery system according to claim 1 further comprising a bypass circuit having a bypass inlet fluidly connected to the one or more evaporators and a bypass outlet fluidly connected to the condenser, the bypass outlet and the expander outlet being fluidly connected at a junction at or upstream of the condenser inlet.
 3. The heat energy recovery system according to claim 2, wherein the port is configured for injection of liquid between the expander outlet and the junction.
 4. The heat energy recovery system according to claim 3 further comprising a further port configured for injection of liquid between the bypass outlet and the junction.
 5. The heat energy recovery system according to claim 4, wherein the port and the further port are integrated into a first component.
 6. The heat energy recovery system according to claim 5, the first component and/or the expander and/or the bypass valve being integrated into a single component.
 7. The heat energy recovery system according to claim 2, wherein the port is configured for injection of liquid downstream of the junction.
 8. The heat energy recovery system according to claim 1 further comprising a pump configured to feed liquid from the liquid supply to the one or more evaporators, the port having a fluid connection to the liquid supply via the pump.
 9. The heat energy recovery system according to claim 8, wherein the further port has a further fluid connection to the liquid supply via the pump.
 10. The heat energy recovery system according to claim 8, wherein the connection and/or the further fluid connection comprises a flow control valve.
 11. The heat energy recovery system according to claim 8, wherein the connection and/or the further fluid connection has a flow path of fixed dimensions.
 12. The heat energy recovery system according to claim 1, wherein the expander has a first inlet and a second inlet fluidly connected to the one or more evaporators, the second inlet being downstream of the first inlet when the expander is driven by the superheated vapor, and a diverter configured to divert fluid flow between the first inlet and the second inlet.
 13. The heat energy recovery system according to claim 12, wherein the diverter is integrated into the expander.
 14. A heat energy recovery system for an engine, comprising: a liquid supply; one or more evaporators configured to heat liquid to a superheated vapor using heat energy from an engine; a pump configured to feed liquid from the liquid supply to the one or more evaporators; an expander fluidly connected to the one or more evaporators and configured to be driven by the superheated vapor, the expander having an expander outlet; a condenser having an inlet fluidly connected to the expander outlet; and a port upstream of the condenser inlet and configured for injection of liquid from the liquid supply to reduce the temperature of fluid entering the condenser; wherein the port has a fluid connection to the liquid supply upstream of the pump.
 15. The heat energy recovery system according to claim 14 further comprising a bypass circuit having a bypass inlet fluidly connected to the one or more evaporators and a bypass outlet fluidly connected to the condenser, the bypass outlet and the expander outlet being fluidly connected at a junction at or upstream of the condenser inlet.
 16. The heat energy recovery system according to claim 15, wherein the port is configured for injection of liquid between the bypass outlet and the junction.
 17. The heat energy recovery system according to claim 15, wherein the port is configured for injection of liquid between the expander outlet and the junction.
 18. The heat energy recovery system according to claim 15 further comprising a first port configured for injection of liquid between the bypass outlet and the junction and a second port configured for injection of liquid between the expander outlet and the junction.
 19. The heat energy recovery system according to claim 18, wherein the first port and the second port are integrated into a first component.
 20. The heat energy recovery system according to claim 19, the first component and/or the expander and/or the bypass valve being integrated into a single component.
 21. The heat energy recovery system according to claim 18, wherein the first and second ports are fluidly connected to the liquid supply via a further junction.
 22. The heat energy recovery system according to claim 21, wherein the further junction is downstream of the fluid connection.
 23. The heat energy recovery system according to claim 21, wherein the first port has a first fluid connection to the liquid supply and the second port has a second fluid connection to the liquid supply, the first and second fluid connections being connected downstream of the further junction.
 24. The heat energy recovery system according to claim 14, wherein the fluid connection comprises a flow control valve.
 25. The heat energy recovery system according to claim 14, wherein the fluid connection has a flow path of fixed dimensions.
 26. The heat energy recovery system according to claim 14, wherein the fluid connection comprises a pump.
 27. The heat energy recovery system according to claim 26 wherein the pump is a jet pump.
 28. A vehicle having an engine and a heat energy recovery system according to claim
 1. 